Reformer distillate as gassing additive for transformer oils

Abstract

This invention relates to reformer distillates as gassing additives for transformer oils. The reformer distillates have a 1-ring and 2-ring aromatics content of at least 98%, and are added such that the transformer oil contains less than 10 wt % of reformer distillate. The invention also relates to a method for preparing transformer oils containing reformer distillates and having excellent gassing tendency, oxidative stability, viscosity and volatility.

1. A transformer oil comprising a dielectric fluid and between 3 and 6 wt %, based on transformer oil, of a reformer distillate, the reformer distillate comprising between 9.6 vol % and 16.9 vol % of C 11  to C 13  alkylbenzenes and between 64.2 vol % and 76.1 vol % of alkylated naphthalenes, based on reformer distillate, wherein the gassing tendency of the transformer oil is between −28.2 and −54.2 μL/min. 
     
     
       2. The transformer oil of  claim 1  wherein the amount of reformer distillate is 6 wt %, based on the transformer oil. 
     
     
       3. The transformer oil of  claim 1 , wherein the total amount of benzene and toluene in the reformer distillate is less than 0.01 wt % and the amount of xylenes in the reformer distillate is less than 3 wt %, based on reformer distillate. 
     
     
       4. The transformer oil of  claim 1 , wherein the C 11  to C 13  alkylbenzenes comprise C 11  alkylbenzene, C 12  alkylbenzene and C 13  alkylbenzene. 
     
     
       5. The transformer oil of  claim 1 , wherein the alkylated naphthalenes comprise 2-methylnaphthalene, 1-methylnaphthalene, 2-ethylnaphthalene, 1-ethylnaphthalene, di-methylnaphthalene, and C 13  alkylnaphthalene. 
     
     
       6. The transformer oil of  claim 1 , wherein the combined sulfur and nitrogen containing compounds in the reformer distillate is less than 10 wppm, based on reformer distillate. 
     
     
       7. The transformer oil of  claim 1 , wherein the dielectric fluid used in transformer oils includes at least one of naphthenic oils, paraffinic oils and synthetic oils. 
     
     
       8. The transformer oil of  claim 1 , wherein the average molecular weight of the reformer distillate is between 100 and 200. 
     
     
       9. The transformer oil of  claim 1 , wherein the transformer oils may contain additives including oxidation inhibitors, pour point depressants, gassing tendency improvers, corrosion inhibitors and metal passivators. 
     
     
       10. A process for preparing a transformer oil which comprises reforming a naphtha feedstream under catalytic reforming conditions to produce a reformate, distilling the reformate to produce a reformate distillate having between 9.6 vol % and 16.9 vol % of C 11  to C 13  alkylbenzenes and between 64.2 vol % and 76.1 vol % of alkylated naphthalenes, combining the reformate distillate having a mixture of C 11  to C 13  alkylbenzenes and alkylated naphthalenes with a dielectric fluid to form a transformer oil wherein the amount of reformer distillate in the transformer oil is between 3 and 6 wt % based on the transformer oil, wherein the gassing tendency of the transformer oil is between −28.2 and −54.2 μL/min.